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I am considering removing my catalytic converters in place of an of road x-pipe. I was told by someone that if you remove the cats, you will have to replace the spark plugs every few thousand miles because the car will run too rich, regardless if you have O2 simulators or not. Some of you have done this modification. Could someone offer some insight on as to whether or not this is true. Also, what gains can be expected from removing them? Is it worth it?
 

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This is a very complex subject because of the complicated OBD-II software in the PCM computer. There have been several previous threads that worked around this topic, and there is a lot of excellent info at the <www.teamzr1.com> site forums, but a simplification follows:

Removing the cats or adding a free flow intake and bypassing the throttle body heater, can increase airflow dramatically through a Z06 motor. This is good, the desired effect, more air = more HP, but the PCM is calibrated for the *all-stock* setup. Part of the PCM software tries to "adjust" (aka re-learn) the AFR back to normal by changing the LTFT parameter (Long Term Fuel Trim).

For example, I lost my cats for a Bassani off-road X-pipe, changed to a Halltech TRIC + Cobra and throttle body heater bypass, and using a Ease PCM scanner, my measured LTFT was 18% lean!! (If it gets to 25% lean, it throws an error code.)

With this 18% lean value, when you go to WOT, the PCM adds 18% *more* fuel to the WOT mixture, and the AFR can go way too rich. There was a recent thread where Doug Rippie reported a Z06 going "pig rich" at WOT with a Blackwing. That's what's happening.

John Rovner at Team-ZR1 (link above) has done a lot of pioneering work with C4s and C5s using a MAF Translator to adjust the LTFT back to near zero, resulting in more spark advance, better AFR at WOT, and *lots* more power. I have tried this and it seems to work.

I'm not an expert in this area, John is, but it appears to me that when you get into the mods that attempt to increase the HP by flowing much more air through the engine, you have to use something like a MAFT trick to get the AFR right. Otherwise the PCM ends up fighting with itself -- the more extra air flow you achieve, the more out of calibration the PCM gets, and the worse results you achieve, at least compared to what they could be.

This is just a simple summary. John has a number of detailed articles on the Team-ZR1 web site that would be well worth your time to study. I also recommend you get an Ease scanner and MAFT to re-calibrate the PCM.
 

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Explanation please

Please explain how the MAFT proceedure works. Does it stay hooked up, do you flash the memory with the new parameters and disconnect it? Is all of this done while driving or on a dyno?
Is it fairly simple to use, and reprogram a Z06 PCM?
Thanks
:cheers:
 
G

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Re: Explanation please

A MAF Translator (MAFT) is just that it is a black box if you will, that you plug in series with the MAF and the cable from the PCM.
It has rotary switches on it that allows you to change the signal the MAF outputs and translates that to a signal so that the PCM re-cals AFR to a value you want it to be.
This means the PCM is still getting a proper signal from the MAF, its just changed as you directed it to bring the AFR to a best performace level since itis NOT the role of the PCM to do that, it's role is more of a EPA manager.

Once installed ( takes only a few minutes to install ) it then works on its own and only changes when you adjust it for a different AFR. Your not flashing the memory, your changing the AFR through the change of the MAF signal being reported to PCM, thus this is a way of making PCM re-cals but doing it from the outside of the PCM, but to a major function the PCM relies on to determine what AFR should be set to.

Once installed, the MAF works when engine is running and PCM never knows it is forcing it to recalibrate AFR.
With proper AFR the engine performs much better for your dialing in a AFR that reduces or rids knock, which increases timing and assures your getting use of max torque your engine makeup has.

Mine has been on for almost a year now and without it I'd be in big trouble for my 372 stroker LS1 was runing way too lean and killing max HP and torque.

A MAFT only costs $175 by the maker Ramchargers. Newest version is 5.2 but to really use it correctly you have to have a PCM scanner so that you can see exactly what AFR, timing, knock, etc is so you know where to set the MAFT switches to get the best performance tune out of your PCM.
To me its the best path rather then some tuner hacking on the PCM code that is EPA protected by law because the MAFT will allow you to always re-tune or fine tune as you wish while maintaining the stock PCM software.

John


fyrcaptain said:
Please explain how the MAFT proceedure works. Does it stay hooked up, do you flash the memory with the new parameters and disconnect it? Is all of this done while driving or on a dyno?
Is it fairly simple to use, and reprogram a Z06 PCM?
Thanks
:cheers:
 

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Re: Re: Explanation please

teamzr1 said:
A MAF Translator (MAFT) is just that it is a black box if you will, that you plug in series with the MAF and the cable from the PCM.
It has rotary switches on it that allows you to change the signal the MAF outputs and translates that to a signal so that the PCM re-cals AFR to a value you want it to be.
This meas the PCM is still getting a proper signal from the MAF, its just changed as you directed it to bring the AFR to a best performace level since itis NOT the role of the PCM to do that, it's role is more of a EPA manager.

Once installed ( takes only a few minutes to install ) it then works on its own and only changes when you adjust it for a different AFR. Your not flahsing the memory, your changing the AFR through the change of the MAF signal being reported to PCM, thus this is a way of makigPCM re-cals but doing it from the outside of the PCM, but to a major function the PCM relies on to determine what AFR should be set to.

Once installed, the MAF works when engine is running and PCM never knows it is forcing it to recalibrate AFR.
With proper AFR the engine performs much better for your dialing in a AFR that reduces or rids knock, which increases timing and assures your getting use of max torque your engine makeup has.

Mine has been on for almost a year now and without it I'd be in big trouble for my 372 stroker LS1 was runing way too lean and killing max HP and torque.

A MAFT only costs $175 by the maker Ramchargers. Newest version is 5.2 but to really use it correctly you have to have a PCM scanner so that you can see exactly what AFR, timing, knock, etc is so you know where to set the MAFT switches to get the best performance tune out of your PCM.
To me its the best path rather then some tuner hacking on the PCM code that is EPA protected by law because the MAFT will allow you to always re-tune or fine tune as you wish while maintaining the stock PCM software.

John
I'm getting there John, bear with me please......

The Ease Scanner would allow you to see in real time what your exact AFR's are, correct?

Then you would plug in the MAFT (the MAFT stays hooked up)
You then can use the MAFT to change the AFR at WOT to compensate for the pig rich conditions from an intake install, correct?
So...... do you have to set the pots / controls on the MAFT each time you drive the car?
Where does the laptop, palm, or PC come into play?

Thanks AGAIN:)
 
G

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Re: Re: Re: Explanation please

Yes the scanner is your eyes into the powertrain and from that window you know now realtime (as engine is running) and overall averages of how tables are being set by the PCM.

Consider fuel trims (short and long term) the scanner allows you to collect the same data these tables produce and from that can tell how the trims are for part throttle or what AFR is like at WOT.

The MAFT has two rotary switches, one controls adjusting the long term fuel trims and the other switch is to adjust AFR during WOT conditions.

Lets assume your LONG term fuel trim AVERAGE is 10% too lean, this means how over time/distance the table averaged out.
Now with the MAFT you set it so that the MAF signal is saying to PCM "Go 10% rich", thus the long term fuel trim (LTFT) is forced to around zero ( for best performance and means engine is not running too roch or lean during part throttle ( TPS less then 80% open) and once it is averaged to zero, LTT will then stay around zero and thus the MAFT continues to function and you ONLY touch the MAFT when you want to make some minor fine tune ( as weather gets hotter, you'll want a summer MAFT setting or maybe when at the race track).

Just think of a MAFT as a new function that allows you to adjust AFR and PCM assumes that is what the MAF is telling it.

The P/C is to run your PCM scanner, it is a windows based product that allows you to see all those functions on the P/C screen, it collects everything the PCM sees/does, allows you to record that while driving and then save it as a recording and replay it later on or e-mail it to someone Like Jim Green, or me and we also can replay it on our Ease scanner or export that recording to import into excel and analyze how all the functions are doing and from that dictate what setting we do on the MAFT to obtain the best PCM calibration for peak performance.

The scanner becomes your test tool like the old days when using a dwell meter or timing light, but at a much larger scale of what you can see. With the pro version of Ease scanner, I can tell everything about your car, right down to how your seats are adjusted or when the last time you changed the oil.

fyrcaptain said:


I'm getting there John, bear with me please......

The Ease Scanner would allow you to see in real time what your exact AFR's are, correct?

Then you would plug in the MAFT (the MAFT stays hooked up)
You then can use the MAFT to change the AFR at WOT to compensate for the pig rich conditions from an intake install, correct?
So...... do you have to set the pots / controls on the MAFT each time you drive the car?
Where does the laptop, palm, or PC come into play?

Thanks AGAIN:)
 

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Jim Green,
How do I know my engine is running rich or lean?. After all my mods I do feel my engine revving much more freer and by the seats of my pants delivering more HP.
 

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Other issues

Hi there,
Just remember that when you hit WOT, you PCM goes to power enrichment, which adds more fuel than is needed to keep the pistons from developing hot spots.
Also, alot of people dont realize that sims on the rear o2 positions will also affect your AFR, as the rear o2s add 25% of the formula for total fuel system compensation.
This is just the way the system works, besttoyou, c4c5:z:
 

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First, let me say that I am still a novice at this MAFT tuning of AFR. John ("TeamZR1") is the EXPERT. He pioneered using a MAFT and scan tool to optimize the AFR and power on C4s and C5s. So what I say may be incorrect in some detail ways. John can comment. He can also add things that I don't know. Also, John is a really nice guy and loves Corvettes.

That said, your question: "How do I know my engine is running rich or lean?. After all my mods I do feel my engine revving much more freer and by the seats of my pants delivering more HP."

The only way to find out if it is running rich or lean is to scan it with a scan tool. I use the Ease scan tool because John recommended it, and he knows a *lot* more about this than I do.

But you are right. When you install a freer flowing intake, you increase the air flow through the engine and it makes more power. You get an increased "SOTP reading".

The question is, is it making as much power as it could if the AFR was optimum? The answer seems to be No. That's what John has done, show us how to optimize the PCM settings with the MAFT so we get substantually more HP than just adding the intake system, or the off-road exhaust, or headers, or a cam, or whatever other mod.

If you are happy with your mods now, you will be even happier after tuning it for optimum AFR. I could tell a difference after installing the intake and off-road exhaust. But there was an even bigger difference after installing and tuning the MAFT. (BTW, I'm not yet finished my tuning -- I need to find a place where I can run at WOT for a longer time than is possible on the highway.)
 

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Jim, Thanks for your advice. I will take the car to be diag.. For what I read, the MAFT it is not difficult to install. But I do not feel 100% at ease fiddling with buttons and doing mayor damage to the engine. Or is it your opinion that in the worst case scenario, just unplug the thing and go back to were I was?
Thanks for your input
 

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Thanks John

Thanks John, I think it finally sunk in:lol:

I have learned a lot of "stuff" reading all the posts here at Team ZR1, and at some of the other "guru's" websites:)
John I filled out a "TEAM" application. You have my email address, so please let me know the pieces parts I need, and who to get them from:)
I feel like I can really talk some s$%t with some of my less knowlegable, mechanically impaired local Corvette buddies:lol:
(they were all aghast that I installed my Ripper, and have now progressed to installing a T1):D wait till they hear me talking about adjusting AFR's :D
THANKS again:)
:cheers:
 
G

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Re: Thanks John

You'll get up to speed quickly, that what we're all about, exhanging info and we all end up for the better.

To learn how all this OBD-II/EPA functions work in detail I suggest people reading two good books, both about 400 pages.

Get
OBD-II Daignostic & Repair for Domestic Vehicles by Jendham, Inc

URL=http://jendham.com]OBD-II Book[/URL]

2nd book:

"Corvette fuel injection & electronic engine management."
Can be gotten through Amazon.com

The 2 books tie it all together and give you a boat load in knowledge helping you control your engine and not the PCM.
I fired the team's e-mail system up for you so you can link up
with all the teammates.


fyrcaptain said:
Thanks John, I think it finally sunk in:lol:

I have learned a lot of "stuff" reading all the posts here at Team ZR1, and at some of the other "guru's" websites:)
John I filled out a "TEAM" application. You have my email address, so please let me know the pieces parts I need, and who to get them from:)
I feel like I can really talk some s$%t with some of my less knowlegable, mechanically impaired local Corvette buddies:lol:
(they were all aghast that I installed my Ripper, and have now progressed to installing a T1):D wait till they hear me talking about adjusting AFR's :D
THANKS again:)
:cheers:
 

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Zsin06,

Just to ease your mind, when you first install the MAFT it is set to zero-zero, that is, it is just like it wasn't there. Of course, you don't start changing the settings until you do a scan. That tells you which direction and how far to go to get toward a zero LTFT. You then do another scan to see where you are, etc.

In this whole process you are going toward an ideal AFR, that is, back toward where the car was when it was stock, before the fancy intake.

When we add things like free flowing intake systems, we tend to make the car run leaner (more air, same fuel), so the adjustments tend to be toward the rich direction.

My car was running so lean that John recommended 30# injectors. My Maft is now at 5% richer, and is running much better.

The bottom line is you aren't changing things in a vacuum, so there is no danger of doing any damage to the car.

BTW, I like your car. Nice color, the MY.
 

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Jim, Thanks for your informative reply. Once I do a Diag. I will order the MAFT. I feel much more inform now. This forum and its people are great!!!:)
 

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Butcher recently posted on this same subject.

http://www.z06vette.com/forums/showthread.php?s=&postid=72035&t=844#post72035

It sounds to me like the LS6 is rich from the factory. Makes sense, the cats need fuel to do the secondary reaction. So then the first HP change anyone should make is the Ramcharger MAF translater. Butcher also described a dyno procedure using a wide O2 sensor to adjust the WOT setting.

I think I'm learning something! Thanks for the info.
 

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Have I understood this correctly?

This is a good thread, but I want to confirm what I reading. It sounds like I can alter variables to the PCM using a MAF translater......Like a piggy back computer.
Then I can analyze the affect of the changed variables using a scanning device . I can optimize the "tune" by running the car on a Dyno and watching the results on the scanner? That seems too easy......

Am I reading and understanding this correctly?

Are there any limits to this MAFT? Are there various suppliers of the MAFT and the scanners?

Does the MAFT have any warning signals to notify the driver that it is not working correclty? All electronics eventually fail....

I guess the end result is: If I change the heads and cam, can I use the MAFT and a Dyno to optimize the tune of the new set-up. Do I then not have to pay some "Tuner" to re-flash the computer?
That would be too cool.......

That would mean I could tune my Zo6 to lessen that "stuff" that accumulates across the back of my car during a track session
 

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Have I understood this correctly?

This is a good thread, but I want to confirm what I reading. It sounds like I can alter variables to the PCM using a MAF translater......Like a piggy back computer.
Then I can analyze the affect of the changed variables using a scanning device . I can optimize the "tune" by running the car on a Dyno and watching the results on the scanner? That seems too easy......

Am I reading and understanding this correctly?

Are there any limits to this MAFT? Are there various suppliers of the MAFT and the scanners?

Does the MAFT have any warning signals to notify the driver that it is not working correclty? All electronics eventually fail....

I guess the end result is: If I change the heads and cam, can I use the MAFT and a Dyno to optimize the tune of the new set-up. Do I then not have to pay some "Tuner" to re-flash the computer?
That would be too cool.......

That would mean I could tune my Zo6 to lessen that "stuff" that accumulates across the back of my car during a track session
 

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I have not had any problems.

I was told by a couple of C5 techs that the rear o2's did nothing but monitor the performance of the cats. They do not pull timimg or dump fuel. They just throw codes if the cats are not working correctly. That is the only reason the sims are needed.
 
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